Wireless aerial system



1939. E. c. CORK ET AL I 2,167,709

WIRELESS AERIAL SYSTEM iled March 15, 1937 IN VE N TORS EDWA ,QD CECIL CORK JOSEPH LA DE P4 WSE Y A TTORNE Y Patented Aug. 1, 1939 I UNITEDSTATES PATENT OFFICE WIRELESS AERIAL SYSTEM Edward Cecil Cork, Ealing,London, and Joseph Lade Pawsey, Hillingdon, England, assignors, toElectric & Musical Industries Limited, Middlesex, England, a company ofGreat Britain Application March 15, 1937., Serial No. 130,880 In GreatBritain March 1'7, 1936 5 Claims. (Cl. 250-33) The present inventionrelates to wireless aerial sheath of said feeder, while the other isconsystems and more particularly to dipole aerials nected to the end ofsaid auxiliary conductor. for operation at a relatively shortwavelength. Ihe auxiliary conductor used in systems operat- In thedesign of a short wave aerial for haning in accordance with theinvention may op- 5 dling a carrier wave and wide side bands such aserate in the manner set forth in the above men- 5 are required fortelevision purposes, it is necestioned patent to W. S. Percival et al.sary to reduce the variation of reactance with In order that theinvention may be more clearfrequency asmuch as possible. By using elelyunderstood and readily carried into effect, two merits consisting ofcylinders of large diameter methods of connecting a dipole aerial to afeeder or wide strips, the variation of reactance can be in accordancewith the invention will now be 10 substantially reduced. In many cases,and pardescribed by way of example with reference to ticularly in caseswhere an auxiliary conductor of the accompanying drawing in which,

the type described in the specification of United Figure 1 showsdiagrammatically in perspective States patent to W. S. Percival, et al.,il -2,127,088, a dipole aerial and concentric feeder connected grantedAugust 16, 1938, is associated with the in accordance with theinvention, and 15 aerial end of a concentric feeder, a large amountFigures 2 and 3 show an alternative form of of reactance may beintroduced in the connecconstruction. tions between the aerial elementsand the feeder. Referring to Figure 1 of the drawing, a dipole Thisreactance may be considerably in excess of aerial comprises two hollowcylindrical members that of the aerial elements, in which case the l, 2each provided at one end with a frusto- 20 frequency characteristic ofthe aerial will be 841- conical portion 3, 4. The diameter of thesmaller versely afiected. end of each frusto-conical portion is aboutone It is an object of the present invention to prothird the diameter ofthe larger end and the vervide a new or improved arrangement forcontical semi-angle of the cone is about 55. The necting a dipole aerialto a concentric feeder. larger ends of the frusto-conical portions have25 QQQ t0 the s n i vent in. an i l the same diameter as, and areattached to, the system including a dipole aerial, a feeder and ancylindrical members. The two members I, 2 are auxiliary Conductor whichSBTVBS 0 prevent the shown arranged one above the other, the frustoflowof Current at t frequency 130 e trans conical ends being adjacent oneanother and mitted r r eiv al ne h h h f h f r. separated from oneanother by a distance slightly 30 he ia Of the d e n s be n largegreater than the diameter of the sheath of a n Orderto reduce variationsin reactance of the concentric feeder 5 which is to be connected toserial With Variation in q y, a t n e the aerial. The feeder 5 extendsin a straight troduced due to h i ns e w n h line for only a shortdistance from the end A ip e e ents and the feeder or the auxiliaryconnected to the dipole element l and it is bent 35 Conductor or both.is reduced by disposing the at the point B through a right angle in ahorip ends of the feeder a auxiliary conductor zontal plane. Two furtherright angle bends are so that the connection of the central conductor ofmade t t i t 0 and D, the portion DH the feeder to the auxiliaryconductor is as short being of indefinite length depending upon the asposs b e consistent with maintenance o d position of the transmitter.The points A, B, o, 40 quate insulation between h n of the 21mm D and Hin the feeder all lie in a horizontal plane. iary conductor and Sheath-The dipole elements The distance AB is equal to the distance CD and maybe cylindrical and in such a case their adthe length ABCD is arranged tobe approximately jacent ends are formed as truncated cones equal to onequarter of the operating wavelength. nected to the opposed ends of thesheath and An auxiliary conductor 5 which also has a 45 auxiliarconductor. The ends of the feeder and auxiliarg conductor connected tothe dipole eleiength r g y g ments may be chamfered in order that thedipole mg Wavelengt an 15 2 e i i e 1 m h elements may be disposedsubstantially coaxially. as the Sheath 9 t e feeder 1S hroug In amodified construction according to the ina nght'angle at pomts E and Fand 15 connected vention, the adjacent ends of the dipole elements oneend to the Sheath of the feeder at It are each connected to conductingsurfaces, the arranged t Q= nd that width of which is substantially thesame as the F =B u E d F be a the corners width of the dipole elements,one of said con- 01? a rectangle. The central conductor 1 of the ductingsurfaces being connected to the end of the feeder projects beyond theend of the sheath and 55 is connected to the end of the auxiliaryconductor B.

The spacing between the end G of the auxiliary conductor and the end Aof the sheath of the feeder, is made as small as possible in order tokeep the reactance of the connections to the members of the aerial assmall as po'ssible,but must be sufficiently great to prevent sparking.

In one particular case the variation of aerial reactance with a certainchange of frequency was 5 ohms due to the reactance of the aerialitself, and the increase when connected to the feeder due to thereactance of the necessary connections was found to be small comparedwith 5 ohms. It will be seen that a system of this type is symmetricalabout the vertical plane through H, D and A and also about the plane ofthe feeder.

In a modification of the arrangement described with reference to Fig. 1of the drawings, the feeder is bent at B but, instead of being bent at Cand D, extends away from the aerial in a straight line BCH. Theauxiliary conductor is bent as before at E and F and extends to and isconnected to the sheath of the feeder at C. The lengths ABC and GFECrequire to be slightly different from the value of these lengths in thepreviously described arrangement.

The form of connection shown in Figure 2 differs from that shown inFigure 1 in that the dipole elements are enabled to be arrangedcoaxially one above the other by chamfering the ends of the feeder andauxiliary conductor respectively. In other respects the details ofFigure 2 are as shown in Figure 1. It will be seen that the constructionshown in Figure 2 permits the ends of the feeder and auxiliary conductorto be brought close together, thereby keeping to a low value anyreactance introduced by the connection between the central conductor ofthe feeder and the auxiliary conductor.

Referring to Figure 3 of the drawing, the connection between aconcentric feeder provided with an auxiliary conductor and a dipoleaerial is shown effected by means of a length of open line. The aerialcomprises two cylindrical members 2 mounted one above the other andcoaxially with one another, their adjacent ends being close together andeach having a wide copper strip 8, 9 attached thereto. The strips mayhave a width equal to the diameter of the cylinders, for example, one ortwo feet. The strips extend, parallel with one another, horizontallyaway from the aerial and have their other ends connected respectively tothe sheath of the feeder 5 and to the end of the auxiliary conductor 6to which the central conductor 1 is also connected.

The auxiliary conductor 6 is of the same external dimension as thesheath of the feeder and has a length approximately equal to one quarterof the operating wavelength. It is disposed substantially parallel tothe feeder and the end not connected to the dipole element 2 isconnected to the sheath of the feeder.

The two strips form a line of low characteristic impedance between thefeeder and the aerial. The distance between the strips is preferablyjust suflicient to prevent sparking and may be of the order of 1 inch.

Arrangements according to the present invention are of particular use astransmitting aerials but they may also be used for reception. It will beunderstood that although particular shapes of dipole elements have beendescribed, any desired practical shape presenting a large surface may beused.

We claim:

1. An aerial system comprising a dipole aerial the elements of whichhave a large surface area, a feeder for said aerial including aconductor and a conducting sheath surrounding said conductor, anauxiliary conductor associated with said sheath for preventing currentsof the operating frequency from flowing over the outer surface of saidsheath, said auxiliary conductor being arranged for the greatest portionof its length parallel to said sheath and having a length substantiallyan odd integral multiple of a quarter of the Wave length at which thesystem is arranged to operate, one end of said auxiliary conductor beingconnected to said first mentioned conductor and positioned closelyadjacent the end of said sheath and opposed thereto, the other end beingdirectly connected to the outer surface of said sheath; the adjoiningends of said dipole elements being connected to the opposed ends of saidsheath and said auxiliary conductor.

2. An aerial system comprising a dipole aerial the elements of whichcomprise cylinders of large diameter to reduce variations in reactanceof the aerial with variation in frequency, a feeder for said aerialincluding a conductor and a 'condut ing sheath surrounding saidconductor, an auxiliary conductor associated with said sheath forpreventing currents of the operating frequency from flowing over theouter surface of said sheath, said auxiliary conductor being arrangedfor the greatest portion of its length parallel to said sheath andhaving a length substantially an odd integral multiple of a quarter ofthe wave length at which the system is arranged to operate, one end ofsaid auxiliary conductor being directly connected to the outer surfaceof said sheath, the other end of said auxiliary conductor beingpositioned closely adjacent the end of said sheath and opposed thereto,said end being connected to said first mentioned conductor, the adjacentends of said dipole elements being connected to opposed ends of saidsheath and said auxiliary conductor,

said adjacent ends being formed as truncated cones whereby the reactanceintroduced due to the connections is reduced.

3. An aerial system comprising a dipole aerial the elements of whichcomprise cylinders of large diameter to reduce variations in reactanceof the aerial with variation in frequency, each of said cylinders havinga length equal to one-quarter of the length of the operating wave, afeeder for said aerial including a conductor and a conducting auxiliaryconductor being directly connected to the outer surface of said sheath,the other end of said auxiliary conductor being positioned adjacent theend of said sheath and connected to said first mentioned conductor andmeans for coupling said feeder to the elements of said dipole comprisinga pair of closely spaced parallel conducting plates, the widths of whichare substantially the same as the width of the dipole elements, one ofsaid plates being connected to the end of said sheath and the other tothe end of said auxiliary conductor said pair of plates forming a lowimpedance connecting line between said feeder and said aerial.

4. An aerial system comprising a half wave dipole aerial the elements ofwhich have a large surface area, a feeder for said aerial including aconductor and a conducting sheath surrounding said conductor, anauxiliary conductor associated with said sheath for preventing currentsof the operating frequency from flowing over the outer surface of saidsheath, said auxiliary conductor being arranged for the greatest portionof its length parallel to said sheath and having a length substantiallyan odd integral multiple of a quarter of the wave length at which thesystem is arranged to operate, one end of said auxiliary conductor beingconnected to said first mentioned conductor and positioned closelyadjacent the end of said sheath and in opposed relationship thereto, theother end being directly connected to the outer surface of said sheath,the adjoining ends of said dipole elements being connected to theopposed ends of said sheath and said auxiliary conductor, the opposedends of said sheath and auxiliary conductor being chamfered whereby saiddipole aerial elements may be coaxially arranged.

5. An aerial system comprising a half wave dipole aerial the elements ofwhich comprise cylinders of large diameter to reduce variations inreactance of the aerial with variation in frequency, a feeder for saidaerial including a conductor and a conducting sheath surrounding saidconductor, an auxiliary conductor associated with said sheath forpreventing currents of the operating frequency from flowing over theouter surface of said sheath, said auxiliary conductor being arrangedfor the greatest portion of its length parallel to said sheath andhaving a length substantially an odd integral multiple of a quarter ofthe wave length at which the system is arranged to operate, one end ofsaid auxiliary conductor being directly connected to the outer surfaceof said sheath, the other end of said auxiliary conductor beingpositioned closely adjacent the end of said sheath and opposed thereto,said end being connected to said first mentioned conductor, the adjacentends of said dipole elements being connected to opposed ends of saidsheath and said auxiliary conductor, said adjacent ends being formed astruncated cones whereby the reactance introduced due to the connectionsis reduced, the opposed ends of said sheath and auxiliary conductorbeing chamfered whereby said dipole aerial elements may be coaxiallyarranged.

EDWARD CECIL CORK. JOSEPH LADE PAWSEY.

